What is the likely diagnosis and management for a patient with ST elevation in leads V4-6, II, and aVF, indicating inferior and lateral wall myocardial infarction?

ST Elevation in Leads V4-6, II, and aVF: Inferior and Lateral Wall Involvement

This ECG pattern indicates involvement of both the inferior wall (leads II, III, aVF) and the lateral wall (leads V4-6), most commonly caused by either a distal "wraparound" LAD occlusion extending beyond the apex to supply the inferior wall, or less commonly, a proximal RCA occlusion with right ventricular extension. 1

Primary Wall Involvement

• Inferior wall: ST elevation in leads II, III, and aVF indicates inferior wall myocardial infarction 2
• Lateral wall: ST elevation in leads V4-6 indicates lateral wall involvement 1, 3
• This combined pattern represents a distinctive electrocardiographic presentation requiring careful interpretation of the culprit vessel 1

Most Likely Culprit Vessels

Distal LAD Occlusion (Most Common)

• A distal LAD occlusion with "wraparound" anatomy is the most common cause of this pattern, where the LAD extends beyond the apex to supply the inferior wall 2, 1
• When LAD occlusion occurs below both the first septal and first diagonal branches, the ST-segment vector orients more inferiorly, causing ST elevation in both anterior precordial leads (V3-V6) and inferior leads (II, III, aVF) 2
• Progressive ST elevation pattern across precordial leads favors distal LAD occlusion 1

Proximal RCA Occlusion (Less Common)

• Proximal RCA occlusion with right ventricular involvement can produce this pattern, with the spatial ST vector directed inferiorly, to the right, AND anteriorly 2, 1
• This is less common than the wraparound LAD pattern 1

Critical Distinguishing Features

To differentiate between these two culprit vessels, examine the following ECG characteristics:

• Greater ST elevation in lead III than lead II suggests RCA occlusion rather than LAD 2, 1
• ST depression in leads I and aVL favors proximal RCA occlusion 2, 1, 4
• ST elevation in V1 ≥ V3 and lack of progressive ST elevation from V1 to V3 also favors proximal RCA occlusion 1
• Absence of ST depression in leads I and aVL with the inferior ST elevation pattern suggests distal LAD as the culprit 2

Immediate Clinical Actions

Right-Sided Lead Recording

• Record right-sided chest leads V3R and V4R immediately in all patients presenting with this pattern 2, 1
• ST elevation ≥0.5 mm (≥1 mm in men <30 years) in V4R indicates right ventricular infarction 2
• This must be done rapidly because ST elevation in right-sided leads resolves within 10 hours in 50% of patients with RV infarction 2, 1

Risk Stratification

• Patients with this pattern who have RV involvement have smaller infarct size but higher mortality risk 1
• These patients are at high risk for ventricular septal rupture 1
• ST changes in precordial leads V4-V6 correlate with greater myocardial injury and larger distribution of myocardium at risk 3

Reperfusion Therapy Indications

This patient meets criteria for immediate reperfusion therapy (fibrinolysis or primary PCI):

• ST elevation ≥1 mm in two contiguous limb leads (II, III, aVF) 2
• ST elevation ≥2 mm in two contiguous precordial leads (V4-V6) 2
• Presentation within 12 hours of symptom onset provides maximum benefit 2
• Primary PCI is preferred over fibrinolysis when available, as it allows definitive identification of the culprit lesion 5

Antiplatelet Therapy

• Aspirin 162-325 mg should be administered immediately 6, 7
• Dual antiplatelet therapy with clopidogrel 300-600 mg loading dose is indicated for both STEMI management strategies 6
• If proceeding to PCI, consider GPIIb/IIIa inhibitors (eptifibatide) particularly if high thrombus burden 7

Common Pitfalls to Avoid

• Do not delay right-sided lead recording – the diagnostic window for RV infarction is narrow 2, 1
• Do not assume this is simply an inferior MI – the lateral involvement (V4-V6) indicates larger territory at risk 3
• Avoid aggressive fluid resuscitation if RV infarction is present – these patients are preload-dependent and may develop cardiogenic shock with standard inferior MI fluid management 2
• Do not use nitrates in RV infarction – they can cause profound hypotension 2